Need Bestec 450W Power Supply Schematic Diagram

[Galib]

Hi,
I need Schematic Diagram of Bestec 450W ATX Power Supply . If you have, then please share with me .

Thanks
Galib

[shovenose]

Hello,
what's the exact model if this power supply?

[c_hegge]

This won't be easy to find. PSU manufacturers almost never publish their schematics. Otherwise, no-name manufacturers would copy their designs. If you provide us with the model, then I'll try getting in touch with Bestec.

[c_hegge]

The model number is : ATX - 250 - 12Z Rev : C7R . It has 2 Primary ICs and 4 Optocouplers and 3 Controller ICs . The PSU problem is - I am not getting +5VSB and +5V PS_ON . I don't know - Is this PSU need Load to get +5VSB an +5V PS_ON ??

I have Uploaded the Image at Imageporter.com of this PSU . Please have a look .....

Primary Section :



Controller Section :



Output Section :



If you have schematic of this model then Please share with me .
And any feedback about this Problem and solution will be highly appreciated .

Thanks

[c_hegge]

That's a 250W, not a 450W.

The problem is more than likely a bad capacitor near the primary heat sink, more specifically, the one circled in this picture. Myself and others have had the exact same problem with the same power supply and that was the problem. I realise that the capacitor in your unit isn't bulging like it is in the pictured unit, but it your unit looks like it has an OST brand capacitor in that position, which don't often bulge when they fail. I recently repaired a Bestec ATX-300-12Z (the 300W version of this) which had the same problem, even though none of the capacitors were bulging.

Also, could you please upload pictures here? The links in those pictures point to an objectionable page, so I have removed them.

[shovenose]

Yes, PLEASE use our forum image upload attachment function... external image hosting is a security risk and slows our site down.
Thank you very much!
-shovenose

[Galib]

Firstly, I tried to upload those Images in this site . But being for my slow net speed, I was unable to upload image in this site . This is why I used External link . Again I tried to upload but all in hail . I have just manage to upload the Suspected Capacitor images by spending half an hour .

But the Capacitor seems to be fine and bulging is not visible .

What will I do ?? Will I replace that capacitor .

Honestly speaking - I am not understanding this PSU - how it is working - specially +5VSB unit !!! How it is delivering 2A current through 4 Optocouplers !! My head is spinning !!

Thanks

[Galib]

And Yes, This PSU is 100% same as yours .

[c_hegge]

That PSU uses a small switching IC located in between the primary heat sink and the smaller transformer, as opposed to the transistors used in some other power supplies. These circuits are more reliable than transistor based ones, and don't overvolt when the capacitors go bad. They just stop running instead.

Yes, I know the cap looks fine, but it's an OST brand. It's VERY common for them to go bad without any visible signs of it, so I'd try replacing it.

The smaller transformer is actually what delivers the 5vsb, not tht optocouplers. they are on the feedback circuit.

[Galib]

Thanks c_hegge . Let me to change the capacitor . I will come back several hours later along with the result . Till then bye .